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Cut blasting, a critical aspect of single-sided blasting in underground rock engineering, significantly influences tunnel excavation speed. This study investigates the characteristics of two traditional cut blasting patterns: center empty hole and center charge hole, through on-site blasting experiments. Employing a 3D laser scanner, post-explosion cavity features are quantitatively analyzed in terms of length (L), area (S), and volume (V). The results reveal that cavity volume variation with depth adheres to the equation y = Ax^B (B < 1), and that the center charge hole cut blasting notably expands the cavity bottom. To optimize cut blasting effectiveness, numerical simulations utilizing the smooth particle hydrodynamic finite element method (SPH-FEM) were conducted. Initially, recognizing that cavity formation of the first blasthole presents the greatest challenge in cut blasting, the influences of hole diameter and hole spacing on the first blasthole's explosion cavity size and rock fragmentation were investigated. The results indicate that within a reasonable design range, large-diameter empty holes produce a "U"-shaped cavity in the first blasthole. Moreover, cavity area increased with increasing hole spacing for large-diameter holes, which increased by 14.8%–35% compared with the small-diameter empty holes. However, particle throw distance decreased with increasing hole distance. Subsequently, to improve the overall cavity effect of the center charge hole cut blasting, the influences of bottom charge length within the empty hole and detonation sequence were examined. The results demonstrate that incorporating a bottom charge in the empty hole increased the overall throw effect by 8.6%–21.8%, with the bottom of the particles projected up to 11.7 times the distance achieved without the bottom charge. Optimal results were achieved when the bottom charge of the empty hole was detonated last within the cut blasting sequence. Highlights: Quantitative analysis of on-site cut blasting is conducted; A physical model for the first blasthole blasting process is proposed; The influence of empty holes on the first blasthole is systematically studied; Suggestions for improving the blasting effect of central cut hole are proposed and verified. [ABSTRACT FROM AUTHOR]

Given the significantly large deformation and high strain exhibited by explosively formed projectiles (EFP) in penetration, their penetration performance into multi-layer targets differs from that of ordinary bullets or rigid projectiles. Therefore, it is necessary to investigate the ballistic performance and the damage mechanism of target deformation when an EFP penetrates a multi-layer target. This study conducted high-velocity impact tests of EFPs on four types of multi-layer steel targets, analyzing the damage morphology and deformation characteristics of multi-layer steel targets subjected to EFP penetration from both macro and micro levels. To investigate the anti-penetration performance of more target combinations at different EFP velocities, an accurate symmetrical finite element model of EFP penetration into multi-layer targets was established using Autodyn 16.0 finite element software and the SPH-FEM algorithm based on the symmetrical characteristics of the EFP and target structure. The experimental and simulation results showed that for a three-layer composite target, when the thickness of the middle layer remained constant, using the target layers with a front–rear target thickness ratio of less than one was beneficial for enhancing the anti-penetration performance of the targets against EFPs; when the EFP velocity was low and the residual velocity for penetrating a single-layer target was no more than 200 m/s, the anti-penetration performance of the two-layer target was optimal. When the EFP velocity exceeded 1500 m/s, the single-layer target exhibited the best anti-penetration performance to the EFP, and the more layers, the smaller the ballistic resistance. When the number of layers was more than six, the ballistic resistance of the multi-layer targets gradually tended to remain constant. [ABSTRACT FROM AUTHOR]

In this study, experimental and numerical investigations have been done to explore the effect of the particle properties on the erosion behavior of aluminum alloy during the abrasive air jet machining (AAJM) process by using the novel medium-hard amino thermoset plastic (ATP) and conventional super-hard alumina (Al2O3) particles. In the numerical simulation, a novel linear elastic material model with the failure standard was proposed to define the ATP particle and the conventional rigid material model was used to define the Al2O3 particle. Meantime, the smooth particle hydrodynamics (SPH) interpolant with the moving-least-squares method was used to establish the impact target model. Then, a multi-particle impact model based on the SPH and finite element coupling method (SPH-FEM) was further developed to investigate the particle impact process. It indicates that the SPH-FEM method can be used to simulate the erosion behaviors of the aluminum alloy during the AAJM process by using not only the super-hard Al2O3 particle but also the medium-hard ATP particle, and the simulation results are fundamentally consistent with the experimental ones. The results demonstrate that the effect of particle hardness on erosion behavior is much greater than that of compressive air pressure. Furthermore, there exists an optimal impact angle where the surface material can be removed by chip formation resulting in the maximum material removal rate, and the surface erosion behavior can be accurately predicted by simulation. Moreover, with the particle hardness increasing, the optimal impact angle would be reduced accordingly. [ABSTRACT FROM AUTHOR]

Flow slide is a flow-type landslide, which has high mobility and is destructive to the downstream infrastructures and buildings. In this study, a numerical method is presented to simulate the runout process of flow slide, and the interactions between flow slide and buildings on three-dimensional terrain considering the destruction process. In this proposed method, the flow slide is simulated by smoothed particle hydrodynamics (SPH) and the buildings are simulated by the finite element method (FEM). A node-to-surface contact algorithm is adopted to transfer displacements and contact forces between the flow slide and the buildings. An element erosion algorithm is adopted to simulate the destruction process. The method is validated using an analytical solution to dam break problem and the experimental results in two flume tests. A catastrophic flow slide involving building destruction is then simulated to further test the model performance. The flow depth, flow velocity, deposition area, and building damage degree are all reasonably simulated. The typical destruction process of buildings and patterns of the flow slide are also identified. The method will contribute to a better understanding of flow-structure interactions and is a promising tool for hazard analysis and mitigation. [ABSTRACT FROM AUTHOR]

On the basis of experimental verification, the methods of smooth particle hydrodynamics (SPH) and finite element methods (FEM) were used to study the process of abrasive jets cutting rock under confining pressure conditions. The results show that the failure of rock was mainly due to compressive and shear stresses, while the propagation of cracks was dominated by tensile stress. Under confining pressure, the cracks in rocks were mainly horizontal. The damage depth significantly decreased with increasing confining pressure, while the damage width first decreased and then increased. The critical distance between two slits without penetration is four times the diameter of the abrasive jet. When the cutting direction of the abrasive jet was perpendicular to the maximum stress, the relief range of the confining pressure formed was larger. The results have certain guiding values for revealing the mechanism of abrasive jet impact rock breaking and engineering applications. [Display omitted] • The process of an abrasive jet moving cutting rock under confining pressure was studied. • The unloading of confining pressure during abrasive jet cutting of rocks was studied. • Analyze the optimal spacing of abrasive jet cutting from the aspect of crack penetration. • By comparing and analyzing the influence of confining pressure factors on crack propagation. [ABSTRACT FROM AUTHOR]

Use of abrasive water jet (AWJ) to break rock is a promising technology for improving the speed of tunnelling hard rock roadways. In this study, smooth particle hydrodynamics (SPH) and the finite element method (FEM) were coupled to develop a method that was used to simulate the abrasive water jet slit rock. The failure patterns and crack evolution were analysed. Moreover, the effects of parameters of AWJ on rock slit were studied. Furthermore, the motion behaviour of abrasive particles after collision with hard rock is discussed. The results indicated that the optimum mass concentration and diameter of AWJ were 15% and 1.6 mm, respectively, and the depth of slits cut in rocks increased nonlinearly with increasing pressure. Instantaneous failure and multi-step cumulative failure occurred at the centres and edges of rock fractures, respectively. For impacts at large incident angles, the cumulative damage velocities were greater for the central cracks than the radial cracks. The impact velocity had the greatest effect on the propagation of the central cracks, while the effect on the radial cracks was relatively small. The equivalent stress caused by impact was the primary reason for the failure of rock elements at the main impact site, and the cracks in rock were mainly caused by tensile stress. The damage of rock elements accumulated in steps similar to the shape of stairs. Damage accumulated faster when the pressure peak was large and the pressure undulated frequently. The findings of this study provide a theoretical reference for optimizing the parameters of AWJ and increasing the speed of excavating in hard rock. [Display omitted] • The best parameters of abrasive water jet rotating grooved rock were determined • The damage features of rock slits include instantaneous damage and stepped rise. • The central crack is sensitive to the impact angle, and the damage raises faster. • Multiple factors caused rock damage, and crack mainly depends on the traction. [ABSTRACT FROM AUTHOR]

Abstract: A two-dimensional SPH–FEM model is proposed to investigate its application in the fluid–structure interaction (FSI) problem. The fluid model is based on the theory of Smoothed Particle Hydrodynamics (SPH) and the structural dynamics employ a large-deformation Finite Element Method (FEM). This paper describes the basics of both SPH and FEM models and presents the development of a loosely coupled SPH–FEM model. Validation results of two benchmark FSI problems are illustrated. The first test case is flow in a sloshing tank interacting with an elastic body (Souto-Iglesias et al., 2008) and the second one is dam-break flow through an elastic gate (Antoci et al., 2007). The results obtained with the SPH–FEM model show good agreement with published experimental results and suggest that the SPH–FEM model is a viable and effective numerical tool for FSI problems. [Copyright &y& Elsevier]

Composite laminates can potentially reduce the weight of aircrafts; however, they are subjected to bird strike hazards in civil aviation. To handle their nonlinear dynamic behaviour, in this study, the impact damage of composite laminates were numerically evaluated and designed by means of smoothed particle hydrodynamics (SPH) and the finite element method (FEM) to simulate the interaction between bird projectiles and the laminates. Attention was mainly focused on the different damage modes in various laminates' plies induced by bird impact on a square laminated plate. A continuum damage mechanics approach was exploited to simulate damage initiation and evolution in composite laminates. Damage maps were computed with respect to different ply angles, i.e., 0°, 45° and −45°. The damage distributions were comparatively investigated, and then the ply design was considered for crashworthiness improvement. The results aim to serve as a design guideline for future prototype-scale bird strike studies of complex laminated structures. [ABSTRACT FROM AUTHOR]